Fungal Contamination in Public Buildings: Health Effects and Investigation Methods

Abstract

The word “mold” is a non-scientific term that in popular parlance generally refers to members of a few dozen filamentous fungi. Mold growth on building surfaces not only damages these surfaces, but also affects air quality as intact spores, as well as spore and mycelial fragments, are dispersed in the air. These can be inhaled depending on their size and concentration. Exposure to mold is associated with increased rates of respiratory disease.

This document is a revision of an earlier version published by Health Canada and the Federal-Provincial Advisory Committee on Environmental and Occupational Health (CEOH) in 1995. The intent is to update the information and to reconcile certain practical aspects of the document with newer publications from the American Conference of Governmental Industrial Hygienists (ACGIH), the American Industrial Hygiene Association (AIHA) and other cognizant authorities. The purpose of this document is to assist front-line public health workers in the management of potential health risks associated with fungal contamination in public buildings. The report consists of two parts:

1. A review on health effects of indoor molds
2. A guide for the investigation of mold contamination in non-industrial workplaces

1. Health Effects of Indoor Molds

The 1995 review concluded that “. . . epidemiological studies have consistently detected an association with respiratory symptoms and home dampness and mold growth, but causality in these studies has not been established.” The purpose of this section is to update the CEOH document by reviewing the research published from 1995 to 2001 on health effects of exposure to molds in residences and non-industrial workplaces (mostly office buildings and schools), and to determine whether the current evidence warrants more definitive conclusions.

Major findings from this review are:

• Eight cross-sectional studies investigated the relationship between indoor mold and respiratory, allergic or irritation symptoms, four of which found significant association between mold exposure and either physician-diagnosed asthma or asthma-related symptoms (cough, wheezing or breathlessness).
• Seven case-control studies investigated the relationship between mold and asthma, most relying only on self-reports to assess both mold exposure and health outcomes. One of these studies found a significant association between “mold or dampness” and asthma; another found a significant association between mold and asthma but did not assess dampness; three found significant associations between mold and asthma (one of them after controlling for dampness) but not between dampness and asthma; and two found significant associations between dampness and asthma, but not between mold and asthma.
• To date, no cohort studies have been published on the association between residential mold exposure and asthma, although a published study has found an association between mold exposure at school and childhood asthma. There is presently an ongoing cohort study in Prince Edward Island, Canada.
• Several experimental studies with animal models exposed to fungal cells, antigens or constituents have found effects similar to those observed in humans in epidemiological studies, such as eosinophilia and increased serum IgE.

Several of the studies reviewed were limited by the methods used: exposure and outcome assessment based on self-reporting; no quantitative exposure assessment (and therefore no determination of a dose–response relationship); possible confounding by other biological agents; and potential response bias.

Only in a few studies reported to date has an independent effect of mold on asthma and upper respiratory health been demonstrated. Therefore, from epidemiologic data alone, it is difficult to assess the population health consequences of the material growth of indoor molds. It is known, however, that exposure to fungi in occupational environments causes allergic and toxic diseases. Adverse effects of fungi have also been seen in inhalation studies using animal models. Therefore, further investigation of health effects of indoor fungi using improved exposure and health outcome assessment methods is needed to resolve uncertainties. As established by the CEOH in 1995, current knowledge indicates the need to prevent damp conditions and mold growth and to remediate any fungal contamination in buildings.

2. Investigation of Fungal Contamination in the Non-Industrial Workplace

It cannot be emphasized enough that the best way to manage mold growth is to prevent it before it occurs. The essential elements of a prevention strategy are control of moisture, timely remediation of any water leakage, and adequate maintenance of heating, ventilation and air conditioning (HVAC) systems

The goals of a mold investigation are to:

• establish the cause, nature and extent of fungal contamination;
• assess the risk of adverse effects on the health of building occupants;
• manage the microbial problem(s); and
• return the building to a satisfactory level of performance.

The first step in investigating a building for microbial contaminants is an informed inspection. Mold contamination can arise from condensation, floods and various types of leaks. Investigation of mold problems requires a thorough knowledge of the design of the building envelope and the types of failures that result in condensation and water leaks. Where there is probable cause to believe that there is appreciable mold behind wall cavities, physical inspections should be performed by opening up the hidden area.

Air sampling is appropriate either during or following the inspection. The main purpose of such sampling is to identify contamination that would not be visible without destructive testing and to document air contamination. Air samples should be taken during normal activity in the building, while the ventilation system is operational. They should be collected simultaneously inside and outside the building to enable indoor–outdoor comparisons. The basis of the current methods for interpreting the results of air sampling is a comparison of the diversity of the fungi inside with outdoor air samples.

Sticky surface samplers are increasingly used in mold investigations. Advantages of data from properly collected and analyzed sticky surface samples are twofold: the results are available within a day and in situations when there is a high percentage of non-viable spores in the air, the data are more reliable.

Once the investigation is completed, fungal damage should be expeditiously remediated using state-of-the-art protocols such as those developed by the New York City Department of Health and the ACGIH. As well, quality assurance should be carried out according to standard protocols such as those of the AIHA.

Communication with buildings managers and occupants should be maintained throughout the investigation.